Optical recording media have spread widely generally because of their superiority such as high recording capacity and non-contact write/read system. Recordable optical disks such as WORMs, CD-Rs, and DVD±Rs record information by irradiating a very small area of the optical recording layer with a focused laser beam to change the properties of the irradiated area and reproduce the recorded information making use of the difference in reflected light quantity between the recorded area and the non-recorded area.
Wavelengths of semiconductor lasers used in writing and reading information on the currently available optical disks of the type described are in the ranges of 750 to 830 nm for CD-Rs and of 620 to 690 nm for DVD-Rs. In pursuit of a further increased capacity, optical disks using shorter wavelength lasers have been under study. For example, those using a write wavelength of 380 to 420 nm have been studied.
Optical recording media for short wavelength writing light that have been proposed to date include those containing a cyanine compound having a specific structure disclosed in Patent Document 1, those containing a hemicyanine dye disclosed in Patent Document 2, and those containing a trimethine cyanine dye described in Patent Document 3. These compounds, however, are not always good for use in an optical recording medium for shorter wavelength recording in view of their absorption wavelength characteristics or insufficient solubility or light resistance.
Patent Document 1:JP 2001-301333A
Patent Document 2: JP 2001-342365A
Patent Document 3:JP 2004-98542A